1. Field of the Invention
This invention relates to thermal, gravity-actuated devices, such as thermal converters, engines, etc., and in particular to solar, differential-temperature engines having a movable solid weight which is shifted in direct response to pressure changes between separate vapor chambers, each containing a volatile fluid, oppositely disposed on a rotor relative to the rotor's axis of rotation.
2. Description of the Prior Art
Various types of converters are known for transforming heat energy into mechanical energy. One type of converter, known in the art as a differential-temperature converter or engine, operates on the basis of a vapor pressure differential between a warm vapor chamber and a cold vapor chamber. The operation of the engine requires gravitational forces, an evaporation of the liquid in the warm chamber, and a condensation of the vapor back into a liquid in the cold chamber. The increasing weight of the condensed liquid causes the pivoting of the system about a rotation axis.
Converters of this type are described, for example, in U.S. Pat. Nos. 4,145,890 and 4,195,486.
Other typical systems of this type include a closed loop circulation of the fluid which is vaporized in vapor chambers, discharged as a high pressure gas to a condenser, and returned as a liquid. The high pressure gas is used to drive a turbine or other rotary machine (see U.S. Pat. No. 4,143,517).
Generally, these differential-temperature engines are constructed by providing a rotatably mounted rotor that supports a plurality of such chambers which are alternately or consecutively exposed to a heat source.
Cyclical vapor pressure changes between the chambers result in cyclic shifts in the mass of the rotor which produce moments of gravitational force, and hence rotation of the output shaft to which the rotor is attached.
Some temperature-differential engines utilize liquid to create a weight imbalance in the rotor; the liquid is transferred to a position which is eccentric with respect to the output shaft's axis of rotation.
The transferred liquid may be the pressure-generating liquid itself, see U.S. Pat. Nos. 250,821, 1,115,524, 1,911,456, 3,509,716 and 3,785,144, or it may be an intermediary liquid to which the pressure is transmitted through a deformable wall, such as a membrane or diaphragm, see for example, U.S. Pat. Nos. 3,984,985, 4,019,325, 4,074,534 and 4,121,420.
In engines utilizing a liquid which is transferred from one side to the opposite side of the rotation axis, there is a need to make use of a connecting channel between diametrically opposite chambers of the engines, which complicates the construction of the engine, particularly in view of the fact that this channel must be associated to structural elements supporting said chambers and it must be also provided with means for pivoting the assembly of the chambers as well as the supporting structural elements about a pivot shaft. In addition, the liquid transfer through said channel results in a pressure drop which decreases. Accordingly, the power produced by the engine, which is based on the transfer of liquid under pressure, results in severe leakage problems.
In the engine described in U.S. Pat. No. 3,984,985 there is used an intermediary liquid partially filling a series of adjacent chambers interconnected through a common annular space. In this engine, a considerable amount of power is lost also as a result of the pressure drops through the channels connecting the chambers with the annular space. In addition, it is doubtful that such a system may produce power with a sufficient yield, since a temperature gradient will establish itself between the adjacent chambers, so that the torque available on the output rotatable shaft will be substantially reduced.
Another engine of this type, which comprises a plurality of adjacent chambers distributed at the periphery of a rotor, is described for example in U.S. Pat. No. 4,121,420. However, to cope with the difficulty arising from the establishment of a temperature gradient, the embodiment disclosed in this patent makes use of means for locking the chambers (including bellows) in expanded position until they have traveled over about one half circle. A complicated mechanism is required to lock and thereafter to release the bellows in the convenient position, all of which makes this engine expensive and uneconomical.
The thermal converters or engines according to this invention are considerably simpler and efficient, since they do not require to transfer liquid under pressure, as is the case in the prior art, thus avoiding the power loss by pressure drop and also eliminating the leakage problems associated with such transfer.
Accordingly, the novel engines of the present invention can operate continuously without having to periodically compensate for the liquid leaks; they are considerably simpler, and they can be manufactured at reduced costs for economical, long-lasting operation.